Generally, things keep better if they're in the fridge, are well-sealed and out of sunlight, Pollard says. Following storage instructions on packaging labels will also help food last longer and prevent costly wastage.

And once food is opened and exposed to air, the use-by or best-before dates do not apply.

"Once you open a product, you do with it what you would do with a similar fresh product.

"Many canned foods will last for years and years, but once you open them they may have a shelf life of only a week or so."

Several things contribute to the shelf-life of a product. They include the type of product, how it is stored and whether it is preservative and additive free.

The NZ Nutrition Foundation says: "If in doubt, throw it out."

WHAT ABOUT STORING FOOD?

Poor storage practices can cause bugs such as salmonella and listeria to grow in food, warns the Ministry of Business, Innovation and Employment.

Any raw and cooked food needs to be separated, particularly meat.

The best place to store uncooked meat is at the bottom of the fridge because this is the coldest part, Pollard says.

People should also invest in a fridge thermometer as many are not the right temperature.

"It should be 4C or a little bit less."

Cleaning your fridge regularly and checking that the seals are working properly will also help.